With HDR, brights look brighter and darks look darker for a more natural look.
This video explains people who upgraded from 1080p to 4K often did not notice much difference, until HDR was introduced.
For more info on HDR, here's an article,and a video.
Most other 55-inch TVs with HDR cost $500 and up.
Also, Walmart is selling a LG 49-inch 4K 2160p Smart TV for $328, also has HDR.
Best Buy is also having other last-minute deals available for in-store pickup.